Up a dark and dingy staircase in Causeway Bay, one of Hong Kong’s busiest shopping districts, lies a bookstore that might seem an unlikely tourist destination. While Gucci bags and iPads may be the standard tourist items favored by mainland Chinese, these days, many also return home toting books on China’s politics--books that are banned across the border.

For Hong Kong bookstores, as well as publishing houses, the recent surge in Chinese political intrigue means a serious business opportunity. As a series of leadership splits have shaken China’s top echelons, local shops offering books that promise to pull back the curtain on opaque Chinese politics have been making brisk sales.

“A lot of these tourists stop by here on their way to other sight-seeing destinations,” says a shop assistant surnamed Zheng manning the cash register at Causeway Bay Bookshop. “It’s something they can’t get at home.”

Many of the store's latest bestsellers feature Bo Xilai, the recently purged Chongqing official whose wife is accused of involvement in the murder of a British businessman. At least 12 prominently displayed books are devoted to Mr. Bo, with titles like Bo Xilai’s Crimes, The Inside Story of Bo Xilai’s Fall, Chongqing’s Department of Murder and more. Their cover jackets are heavily cinematic: most feature brooding shots of Mr. Bo, many of them photoshopped, such as Wang Lijun Versus Bo Xilai, in which a bespectacled former chief of police (whose flight to the U.S. consulate in Chengdu first precipitated Mr. Bo’s ousting) glowers menacingly at Mr. Bo through a hole in a brick wall.

Such books have sprung up across Hong Kong in the past month and are being sold everywhere, from newspaper stalls to airport shops. The sudden proliferation seems astonishing, given Mr. Bo was purged from the Communist Party just over three weeks ago. Still, many of the books (which are issued by Hong Kong or overseas publishers) recycle material that’s been previously written about Mr. Bo—including numerous newspaper articles and other content culled from the Internet.

“The books are written with varying quality,” says Ms. Zheng frankly. “Not all of what they publish may be true.”

These days, she adds, there’s too much repetition among books, and much of the content is stale. Still, that doesn’t stop mainland customers from loading up with reading material. Near the cash register, customers flick through their purchases and trade fears that their books might get confiscated if spotted by customs officials, who often seize any books that appear to contain sensitive information about Chinese leadership. Some readers go so far as to put different book jackets on their contraband purchases, the better to avoid getting them confiscated.

Most customers just pick up one or two volumes, but one man—who didn’t want to talk about his purchases—walked out this morning with a stack of ten titles. “People will make special trips to Hong Kong just to buy these books,” comments Ms. Zheng. “Some just pick titles randomly, but some of them really understand Chinese politics better than us and know what they’re looking for,” she says. Previous popular releases include titles like Tombstone—an acclaimed two-volume, over 1,000-page expose by a former Xinhua journalist of China’s government-caused famine in the 1950s—as well as China’s Best Actor: Wen Jiabao, a highly critical account of current China’s premier, both banned on the mainland. Another book, The Secret Journal of Premier Zhao Ziyang, which chronicles the memoirs of Zhao, who was purged and kept under house arrest for 15 years after the 1989 Tiannamen Square protests, has sold some 130,000 copies in Hong Kong since its 2009 publication.

The banned books’ readers “are all from the mainland,” says Ms. Zheng. “Hong Kong people don’t read these things.” For the bookstore, they’re a staple source of profit, accounting for at least 50% of the store’s income, she says.

One customer surnamed Ma, who’d arrived on a business trip from Shanghai, said she wanted to stop in the bookstore to buy something on Bo Xilai for herself, as well as for a friend at home. “I don’t know if what they say is true,” said Ms. Ma. “But I’m still curious to read."